Brother Mine, Sister Mine
by entergrg
Summary: One-shots featuring Holmes siblings in their childhood. May contain OOC-ness. Eurus tells Sherlock he may not have rewritten his memories of her and Redbeard only, but those of their brother, Mycroft, as well. It leads to a revisit of their childhood, before the tragedy hit. Mycroft-centric. **Cross-posted at AO3
1. Prelude

Mycroft is my favorite character in BBC Sherlock, as well as the original novel. I've always wanted to write a story with my interpretation of the eldest Holmes brother. As it is my personal take on Holmes siblings and their dynamics, it contains some (or a lot) of OOC-ness. Please bear this in mind as you read the story!

The story is also cross-posted at AO3.

* * *

"Were you really going to let him die?"

Sherlock asked. He and Eurus had just finished another one of their symphony. His sister stared at him unblinkingly from across the glass wall.

"Yes."

"Why? Why do you hate him?"

"Why not?"

"Well, enlighten me," Sherlock scowled.

Eurus smiled.

"You've always been my favorite, Sherlock."

"Enough about me, tell me why you hate Mycroft enough to make me kill him."

"He was never as interesting as you. Nothing seemed to make him spark… he was too soft, sentimental, reserved…." Eurus went on, dreamlike.

"Wait, wait. Soft? Sentimental? Not sure we're talking about the same brother here, sister dear," Sherlock scoffed.

Eurus observed at Sherlock's face, as if searching for something. Then she smiled again.

"Of course. How frail, our brains are. You didn't just forget about me, you forgot about Mycroft too, haven't you?"

"I didn't forget, I rewrote the memories. And it was only about you and Redbeard, I remember everything else. Crystal clear," Sherlock scowled.

Eurus just kept on smiling, her eyes twinkling in sudden merriment.

" _Sleep, my love, and peace attend thee—_ " Eurus started to sing in a soft alto.

The simple melody of a lullaby washed over Sherlock.

It brought up so many emotions and memories that they were all tangled together, nothing tangible and all mixed up into a confusing stretch of darkness. Then Sherlock suddenly opened his eyes in a small room in his mind palace. A place he didn't even know existed.

Young Mycroft stood in the middle of the room, his arms carrying Sherlock sniffling against his chest.

" _—_ _All through the night, guardian angels and God will send thee, all through the night—_ "

Mycroft softly hummed the lullaby as he drew slow circles on the small boy's back.

Suddenly, the door opened and a young girl—Eurus—came in.

"Eurus, please. You must stop hurting him," Mycroft pleaded.

"But he liked it. We had fun together," Eurus said, her voice strangely void of emotion just like how it was now.

"If he's in pain, that's not fun. It's not fun at all. Please, sister dear."

Sherlock, who was half falling asleep at that point, stirred and saw Eurus.

"Go 'way!" Fresh tears came down his already tear-streaked face.

"Please Eurus, leave. I'll find you in a bit, okay?"

Eurus observed them in silence. Then she turned around and left, door closing in a loud bang behind her.

"Shh, it's alright, brother mine," Mycroft whispered and resumed his singing.

* * *

Well, that was short. It was a prelude of sort to the rest of the one-shots, which I'll begin posting soon.

By the way, does anyone recognize the lullaby? :)


	2. Chapter 1

Mycroft's POV.

The beginning of the Holmes siblings and a little bit of Sick!Sherlock and BigBrother!Mycroft :)

* * *

Mycroft clearly remembered the day he became a brother—a big brother. He waited patiently as the relatives took their turn at cooing and making baby talks at Sherlock, and was finally rewarded with the very first view of him.

He was ugly. He actually reminded Mycroft of a troll doll, one of those horrid things they sold in toy stores that made you wonder why anyone would willingly pay any money for it. His face was all wrinkly and red, with eyes tightly shut despite all the commotion going around him. From time to time his short arm or leg would fitfully lash out at nothing.

And Mycroft instantly fell in love with him.

He gently stroked the baby's palm, and the baby latched onto his finger with a surprisingly strong grasp. Then he opened his tiny eyes into tiny slits and stared at Mycroft's face.

"Hi Sherlock," Mycroft whispered.

"Oh look at his eyes—they are so blue!" Aunt Marge cried, and that started another round of cooing and baby talks. In their excitement Mycroft was unceremoniously shoved away from the baby. The baby started crying, and Mycroft stood there, listening intently to his brother's voice for the first time.

A year after Baby Sherlock's birth, another baby, this time a girl, came to the family. Everyone was just excited as the last time, and the house was once again filled with happy, cooing relatives. The only difference was that now the house was decorated in blindingly bright pink, as were all the gifts.

Just like the last time, Mycroft waited silently for his turn to be introduced to the newest member of the Holmes family. But this time he had his brother in his arms.

Sherlock frowned and fretted at the commotion. He never liked the crowd or noise. He tugged on Mycroft's shirt collar and whined. His eyes were full of reproach, as if he could not believe his brother was subjecting him to stay in this wretched place.

"Shh, I know Sherl. It'd just be a moment, I promise. Don't you want to see Eurus? You'll like her."

"My, go."

"I'll take you back to your room right after we see her, okay?"

"GO!"

Mycroft let out a small sigh. He found Daddy at the periphery of the crowd and told him that they would be in Sherlock's room. Daddy wasn't happy about them leaving such an important family moment, but relented when Mycroft explained how having Sherlock throwing a fit would not exactly work in favor of the moment.

"He's such a difficult child," his dad murmured.

"He's just a baby, that's all," Mycroft replied as he began to head toward Sherlock's room.

As years went by Mycroft became increasingly aware of how extraordinarily brilliant his younger siblings were. The realization that he was not the only one with gifted intellect in the family brought both relief and terror. He was relieved that he finally found someone with the potential to be his intellectual equal one day. But he was equal parts terrified at having to raise two young brilliant minds. Yes, raise—because his beloved albeit ordinary parents were clueless when it came to looking after these ingenious hellions.

It did not help that Sherlock was a sickly child, and a terrible patient.

Like clockwork, Sherlock went down with flu whenever the weather turned cold. Mummy would force him to bedrest, which the little boy protested with a vengeance. It was always the same routine. Mummy would tuck him in so tightly that Sherlock, in his weakened state, could not easily free himself from the bed. Then he would resort to his best means of attack—his words. He would shout himself hoarse and demand his freedom and autonomy to be returned.

"You stay right where you are, young man, or you're grounded even when your fever's down!" Exasperated, Mummy shouted back to four-year-old Sherlock.

"No! It's so b-o-r-i-n-g lying here. I'll definitely turn into a stupid idiot like everybody else if I stay here and let boredom kill my brain cells. Why can't you see it? It's so awfully BORING here!" Sherlock complained.

"You got your books and toys here! For heaven's sake, what more can you possibly want?" Mummy replied, exasperated.

"I DON'T LIKE THEM!" Sherlock screamed and thrashed about. Mummy stood up from her bedside post and forced Sherlock to stay still, afraid that all the excitement would bring up the fever.

All the while, Eurus stood watching from her corner of the room. Her eyes, shining with fascination, never wandered from Sherlock. To her he was the greatest mystery, an enigma. He always had so many words to say, so many sounds to make. There was just so much energy wrapped in that small frame, that Eurus idly wondered what it would be like to make that energy explode. He was by far the most interesting thing she had ever seen.

"Why do you always have to be so difficult? Look at Mycroft or Eurus, they are practically angels compared to you!"

"Well then, go to them! Leave me alone!"

"Sherlock!"

At that precise moment, the door to Sherlock's room opened, revealing Mycroft. He was just back from school, still wearing a thick coat and carrying schoolbag in hand.

"Mycroft, talk some sense into your brother's head. He is being devilishly difficult," Mummy said, her eyes never breaking contact with those of her younger son.

"Why don't you go downstairs for a breather, Mummy? I'll take care of him," Mycroft said reassuringly, his best boy smile firmly plastered on his face.

Mummy sighed and stood up, giving Mycroft a peck on his cheek.

"Yes, I better get supper going anyway." She then looked around in search of her youngest, and found her standing eerily still at the corner. "Come along, Eurus, let's go with Mummy. Mycroft, call if you need help."

"I will," Mycroft answered and ushered her and Eurus to the door.

The door closed with a soft click. Mycroft let out a long sigh and turned around, shedding his coat. Sherlock watched him petulantly from his post on the bed, arms crossed in a classic show of defiance.

"I'm bored," the boy declared.

"I know. But you'll upset Mummy if you wander around," Mycroft replied as he sat himself on the chair recently vacated by Mummy.

"But there's nothing to do here! I've already taken a nap, re-read my books, memorized the periodic table you gave me, and now I'm bored!"

"Well, good thing then that I came prepared, eh?" Mycroft smirked as he pulled out a book he bought on the way home.

"What's that?" Sherlock asked, his interest instantly piqued. The small boy almost jumped out of the bed as he reached for it.

"It's called Sudoku. I dare you to finish this book by tomorrow evening. Oh, I'm taking it away for supper and night, of course."

Sherlock practically vibrated with thrill as he received the challenge. As soon as he had his hands on the book, he flipped to the introduction, read through the instruction, and looked at the first puzzle with rapt focus. He impatiently stretched his palm towards his brother, who handed him a pencil.

Smiling, Mycroft looked over Sherlock's shoulder.

"You should put five there, not seven."

"Mycroft! Shush!"

Mycroft chuckled in response as he got comfortable in his chair and took out his worn copy of _Odyssey_.

* * *

Baby Sherlock & Big Brother Mycroft are my favorite by far :)

Comments are much appreciated!


	3. Chapter 2

How do you explain pain?

* * *

At a very young age Mycroft had come to realize that his mind worked differently from others. At first he was confused as to why his parents could not see what he could see, or understand what was so plain in his eyes. This generated a deep sense of isolation and alienation, and Mycroft hid his "difference" to fit in with his surroundings. He was determined not to subject his siblings to such fate.

But it was so hard to look after two young siblings when Mycroft himself was nothing more than a child. And how different they were! While Sherlock was like a released bouncing ball in a perpetual motion, Eurus was just like her namesake. She was usually quiet and silent, but blasted everything around her at the most unpredictable moment.

One night, Mycroft awoke with a sudden start. He wasn't sure what woke him, but his heart was racing and he could feel cold sweat breaking out his back.

That was when he heard it—a distant sound of distraught.

Recognizing the familiar sound, Mycroft dashed out of the room in a splint. Following the noise he came to Sherlock's room. What he found there stunned him to the core.

Sherlock was lying on his bed, and on top of him was Eurus with her hands wound around his neck. Sherlock's limbs flailed about as he struggled to get out of her hold. But Eurus was unmoving, seemingly entrapped in how Sherlock's scream wavered and changed as she applied and released force on his throat.

"Sherlock!"

Mycroft ran inside and snatched Eurus' wrists, forcing her to let go of her tight grip.

"My—Mycroft," Sherlock hiccupped and launched himself at his brother. When Mycroft instinctively held him close, the small boy clung to him tightly with quivering limbs. He buried his wet face in the crook of Mycroft's neck and cried.

"Eurus, what on earth were you doing? You hurt Sherlock!"

"I was just playing with him. He was laughing."

"He was not laughing, dear sister, he was screaming! Can't you see how you hurt him?"

After a moment's silent observation, she asked, "Why is he crying?"

"Why he is—Eurus, you practically wrung his neck! When you cause someone pain, that hurts them and makes them want to cry," Mycroft said with a sigh. Now that the initial shock was over, he realized that this was yet another incident of Eurus' terrifying oddity, made even more disturbing by seemingly innocent intent behind it.

"What is pain, Mycroft? I read about it more, but it still sounded too abstract."

Mycroft was forcefully reminded of a similar incident only a few weeks ago. Eurus had cut her own arm until it was bleeding profusely. Horrified, Mycroft had quickly wrapped his handkerchief around the bleeding arm and asked her why she did such a terrible thing. Eurus had replied that she just wanted to see how her muscles worked. When he asked if she didn't feel pain, she had calmly asked back, _"Which one is pain?"_

At that, Mycroft had drawn his baby sister into a tight embrace.

His sister, so brilliant beyond measures, lacked something vital that made people human. It utterly broke his heart. He was at a complete loss; no matter how plainly he explained, she just could not understand what came naturally to most other people. He wanted to help her, help her understand those basic things like love, happiness, and even pain at a visceral level, not just at an intellectual level. But nothing seemed to work.

Because she could not, in her stead Mycroft mourned for her loss of ability to feel, really feel things.

Back to present, Mycroft shook his head in silent despair.

"Dear sister, I'm afraid there are things that you cannot perfectly understand from reading alone. But please, if you want to experiment anything, come to me. Leave Sherlock alone. You like him, don't you? You shouldn't hurt those you love."

"But you're no fun. I like Sherlock. I like it best when he laughs."

"Eurus, dear… please. Please promise me you won't hurt him again."

At his plea Eurus gazed into his eyes. After a while, she blinked and left the room.

"Sherl, you alright?" After seeing her leave, Mycroft turned his attention back to his brother. Sherlock's shaking had subsided, but he still maintained his death grip on Mycroft.

Sherlock jerkily shook his head no.

"Let me see your neck? Did she hurt you anywhere else?"

At Mycroft's continued prodding Sherlock reluctantly let go of his grip. His neck was ringed with rapidly darkening bruises, but thankfully he seemed otherwise intact.

"She hurt me," Sherlock declared. Deep frown decorated his young, tear-streaked face.

"I know, brother mine. What she did was wrong, very wrong. I'm sorry I wasn't there quicker."

"I didn't laugh."

"I know."

"She didn't let me go when I told her to go 'way."

"I'm sorry."

"I don't like her. I'm never gonna play with her again. She's despicable!"

"Sherlock—" Mycroft was about to say that he shouldn't say such things, but let out a deep sigh instead. "Let's get you back to bed for now, okay? I'll talk to her again tomorrow."

"I don't want to stay here. Can I sleep with you tonight?" Sherlock looked up at his brother with big, imploring eyes. His lingering frown seemed to indicate that he saw it a rightful demand after such ordeal.

"Just for tonight. You want me to carry you?"

Sherlock nodded and latched onto his brother again.

" _I_ like you best," murmured Sherlock as he locked his arms around his neck.

* * *

Eurus wasn't attempting to kill Sherlock (if she was, Mycroft wouldn't have left her at that), but, at least in her eyes, merely "playing" with him. I think what makes Eurus more frightening is the seeming innocence behind her twisted acts. Thus, Mycroft is torn between the conflicting feelings of terror and pity.


	4. Chapter 3

I'm sorry it's been a while since the last update. I just wasn't entirely happy with this chapter... I'm still not, but decided to stop holding onto it. I may make some changes later though :) Please let me know what you think!

* * *

Mycroft sat with Eurus in the cozy study of Musgrave Hall. Gentle wind wafted from the open window. Although the temperature was rising with approaching summer, it was still pleasantly cool in the morning. Everything was quiet for once, and Mycroft was glad to share this moment of peace with his sister. In these moments he could dare to hope about melting the steel cold heart of hers and somehow helping her become more… Mycroft wasn't sure what exactly.

"Feelings are so very weird, and unnecessary, don't you think Mycroft? They're just series of neurons firing, and still people live and die by them," Eurus said, a neuropsychology book lying on her lap.

"But still those make us alive and human. Life, I'm afraid dear sister, is filled with unnecessary but very much vital humanness," Mycroft replied.

Eurus was silent for a while, quietly contemplating his words.

"Why do you like us?" She asked as she once again directed her steely eyes at her oldest brother.

"What do you mean?" Mycroft asked back at the seemingly unrelated question, wondering about the sudden turn of her thought.

"Us—Sherlock and me. Why do you like us? Is it because we share the same genetic legacy as you? Are you governed by the altruism evolved for the sake of successful transmission of genes?" Eurus inquired with a detached, almost innocent curiosity. "Is this also one of 'unnecessary but vital humanness?'"

"Does it really matter? Regardless of what the conscious or unconscious reasons are, the fact is I care about you both. Deeply," Mycroft replied, inwardly cringing. Newly entered teenagehood forbade him from making such "sentimental"' speech, but there was no helping it with his sister on such matters. Despite all her brilliance she still had difficulty understanding basic human nature. The best approach, Mycroft had discovered over the years, was to be as frank as possible. No matter how much inner cringing it caused.

"That's very unwise, Mycroft, acting purely on reasons beyond your awareness," Eurus said.

When Mycroft was about to reply, he was interrupted by a whirlwind that was Sherlock. The middle Holmes child barged in, not caring how his forceful entry rattled the nearby cabinet and knickknacks on its top.

"Mycroft! Come play with me!" Sherlock demanded. He was donned in his favorite outfit of the year—pirate's costume. "Victor's coming, and we need you to play the villain!"

"Well, aren't pirates usually the villains? If I'm forced to play with you rugrats, at the very least I should get to be a hero," Mycroft rolled his eyes and grumbled, "and besides, I'm talking with Eurus. Now shoo, go play pirates with your first mate."

"No! You must come!" Sherlock stomped his foot, standing akimbo in an uncanny resemblance to their mother. Successful transmission of genes, indeed.

Mycroft sighed. "Sherlock, really, be reasonable—" he was about to scold him for his manners, but stopped short when he observed his brother's quivering lips and stark white pallor of his face. That was odd, too overdramatic even for Sherlock. "Eurus, please excuse me. And just… know that some facts don't change, regardless of the soundness of reasoning behind them."

Eurus said nothing in return, but simply opened the heavy book again in a silent dismissal.

When Mycroft stood up from his seat, Sherlock grabbed hold of his hand and virtually dragged him out of the room.

"Sherl, wait. Why are you in such a hurry? You'll fall if you don't watch your footing," Mycroft lightly scolded.

"You shouldn't do that," Sherlock shot back.

"Do what?"

"Staying alone with Eurus. Did she hurt you?"

"Did she—no, she didn't. Is that what this is about? Sherl, it's okay, she didn't hurt me. I'm perfectly fine," Mycroft assured.

"Still, don't do that," Sherlock frowned.

"You were worried about me?" Mycroft didn't know whether to be touched or disturbed at the fact that his younger brother felt the need to protect him from their sister.

Sherlock looked up at Mycroft, his annoyed expression clearly conveying that the younger boy thought it was a dumb question. "Told you she was mean. You never listen to me," he grumbled.

During their talk they had reached the hind gate opening towards the beach.

"Well, does that mean I don't actually have to play pirates?" Mycroft asked, one of his eyebrows arching up.

"No. You're not a pirate, remember? You're the villain, the evil governor."

"How thrilling," Mycroft replied with a long suffering sigh.

* * *

A bit of protective Sherlock in this chapter :)


	5. Chapter 4

I apologize for the late update. Life happened... actually it's still happening. I'm not sure when I'll be able to come back next, but please enjoy this chapter in the meanwhile! :)

* * *

Sherlock was bored. It was not an uncommon occurrence (in fact, it happened in a far greater frequency than what the precocious six-year-old would have liked), but it was hard to bear nonetheless. The world was too harsh on him—why give him the brilliance of mind but not enough stimuli to keep him properly entertained? Sherlock had asked Mycroft about this before, and his brother had rolled his eyes at him and shooed him away.

Come to think of it, that was happening a lot more frequently lately too—Mycroft shooing him away whenever Sherlock so much as opened his mouth. He was not some fly to swat away! What did Mycroft know anyway, all he did all day long was sitting around eating and reading. Seriously, Sherlock could not even fathom the boredom that was his brother's life. Nothing, well, except _her,_ seemed to rouse him to action.

Sherlock frowned. He thought Mycroft liked him best! Why didn't he move when it was _him_ demanding attention? Did he not care?!

Indignant and determined to rectify the situation, Sherlock went off in search of his wayward brother.

The first place Sherlock went was the study, Mycroft's natural habitat. But the only thing that greeted him there was a neat pile of newly purchased books, yet to be sorted into apropos places on the bookshelves. This led Sherlock to skip kitchen and backyard, and head straight to his brother's bedroom. If Mycroft had not put away the books by now, it meant only one thing. Daddy must have dragged reluctant but accommodating Mycroft for an early morning hiking again. Although Mycroft humored him, he absolutely abhorred such unnecessary physical exertion and usually went right back to bed after a long bath and hearty breakfast.

True to his prediction, the young boy found his brother sound asleep in his bed. He was even dressed in pyjamas, a clear declaration of his will to sleep. And sleep did he do.

With glee Sherlock rocked on the balls of his feet, thinking of all different ways to startle the unsuspecting, slumbering prey awake. He was about to decide on releasing Victor's pet hamster, which he had graciously let Sherlock borrow for "observations", inside the covers, when he detected something odd on his brother. Upon close inspection, he found that Mycroft's hands and face were dotted with red marks and bruises. His left palm was even thickly bandaged. Judging by the location of the wounds, he must have tripped downhill and slid down a few feet. He bet that his knees, hidden beneath the cover and pyjamas, were bandaged as well.

Stupid, fat Mycroft.

Sherlock plonked himself next to him and slid under the cover. In his sleep Mycroft murmured a protest, but nonetheless shifted to make room for him. Sherlock tucked himself under the older boy's arm and peered through his curly bangs at his sleeping brother.

Lately Mycroft seemed to grow more and more distant, always deeply lost in thoughts. He would sit in one place brooding for hours, which more often than not ended in stress-eating. If Mummy and Daddy wanted him to drop some pounds, they should sort out what vexed him, not force him to go on excursions that cause more damage than good. Sherlock could just picture it in his head—Mycroft tripping over his own feet while contemplating one thing or the other on his way back down from the hike.

Most likely, the subject of his contemplation was their sister.

Sherlock let out a petulant sigh.

Sometimes he wondered what it would be like to be just him and Mycroft. Of course, they had a whole year together before Eurus was born, but that didn't really count because it wasn't like Sherlock could remember it. There was a limit to even his brilliance and eidetic memory. It wasn't that Sherlock hated her. Well, maybe a little. It was hard to like someone who seems to regard you as their favorite chew toy. But she was still his baby sister, and he liked her okay when they were playing violin together.

But still….

It would be a nice change. Being the youngest, and having a big brother only you could rely on. Although Mycroft could be annoying and overbearing, especially when he tried to mother hen him, but frankly he wasn't all that bad. Well, at least sometimes, that is. Like right now, when he made a decent body pillow.

Sherlock's eyelids grew heavier with each passing moment and eventually slid close. Everything was quiet in the room. The rhythmic rising and falling of his brother's chest was comforting and reassuring. Sherlock flung his arm and leg over him and signed in contentment.

"'erlock?"

Mycroft, who roused slightly from the intrusion, murmured the younger boy's name.

As he drifted to sleep, Sherlock could hear the familiar tune of a lullaby hummed softly as Mycroft lightly patted him on the back.

" _Sleep, my love, and peace attend thee—_ "


	6. Chapter 5

I'm sorry for the late update! We now move onto the climax of the story :)

* * *

Nothing was the same after the Redbeard incident. When they all—at least the Holmes brothers—realized that the game had reached its end with Eurus' announcement of Drown Redbeard, Sherlock broke down. He was inconsolable; he refused to eat, cried himself to sleep every night, and screamed in terror and resentment whenever he spotted even a glimpse of his sister.

Mycroft had never hated himself more than he did then.

He felt powerless and weak. Defeated. He was proven inferior to his sister, with dire consequences. It felt like nothing he had experienced before. It terrified him.

Although Mycroft had long suspected that Eurus' genius might take a dark turn, he was sure he could curb it, restrain it. It turned out that even he was powerless when it came to his sister.

He was supposed to be better than this. He was supposed to look after them. He was supposed to be the smartest one, the one in charge, the protector who could protect his siblings from both others and themselves.

But even when he exerted himself to the fullest, he still could not stop Eurus from committing a heinous crime.

Because crime it was. Although no one could hold her responsible because of lack of evidence, Mycroft knew it was her doing. But others seemed to find it hard to imagine that a small, quiet girl like her could kill a boy. Victor was declared missing, and his case was left as a mysterious cold case.

What really terrified Mycroft was that Eurus seemed not at all disturbed by the crime she had committed. She merely seemed a little surprised at Sherlock's vehement reactions. At first Eurus tried to approach him, seemingly wanting to play with him like before. Actually, this was what it was really about: Eurus' jealousy. She was jealous of Victor, who seemed to have robbed her of her favorite playmate. And she did not know how to understand or express it, like she was with any other emotions. Confused at her own feelings, she took destructive measures to rectify it. But when she was met with even greater rejection, she stopped her attempt to gain back Sherlock's attention.

That was what terrified Mycroft the most. He knew his sister and could predict her thought patterns. He knew it was only a matter of time until she decided that Sherlock was useless if he was to keep refusing her the attention she craved. He also knew that he would be powerless to stop her if she chose to take action.

"Mycroft, stay," Sherlock pulled on his brother's sleeve as the older boy stood up from his bedside seat. Ever since the incident, Sherlock had grown clingier than ever. He didn't want to be left alone at all times, and grew restless when Mycroft was out of his sight. One time when Mycroft had gone out of the room to make some tea, Sherlock nearly had a meltdown. Mycroft hurried back after a distress call from Mummy, and Sherlock clung to him and cried that he thought he had disappeared "just like Redbeard."

"I'm only going to turn off the light. It's way past your bedtime, Sherl," Mycroft said as he turned on the bedside lamp before he turned off the ceiling light.

"Stay," the younger boy commanded, his lips pursed in a quivering line.

"All right, all right. Go to sleep, huh?" Mycroft sat back down and lightly ran his fingers through his brother's unruly curls.

Sherlock kept his gaze locked at him until he finally drifted off to fitful sleep. Only when he was sure that the small child was asleep did Mycroft let out a tired sigh.

He had come to a conclusion earlier that day. He knew his parents would not approve of it, but there was no other choice left.

Quietly as not to stir the sleeping boy awake, Mycroft stood up and left the room.

The whole house was silent. Mycroft paused briefly in front of the closed door to his sister's room. A thin strip of light shone under the door. It seemed like he was not the only one still awake. He contemplated going in, but decided against it. He knew his determination would waver if he saw her now. Instead, he resumed his way downstairs.

Mycroft went to the dining room and picked up the landline. Taking in a deep breath, he dialed the number he had memorized many years ago.

 _"_ _Hello?"_ A baritone voice answered the phone. There was no trace of sleep, as if the receiver had been expecting the midnight call.

"Uncle. It's me, Mycroft."

 _"_ _Mycroft! Why, hello, dear. I haven't talked to you in ages. For you to call me at such hour… I see I assumed correctly about the missing child, Victor was it, that case being related to your family,"_ Uncle Rudy said softly, _"I really hoped I was wrong."_

Uncle Rudy was Mummy's oldest brother. He was the only one besides Mycroft to have noticed that something was wrong with the youngest Holmes child. But when he mentioned this to Mummy, she was greatly offended. They had a serious argument that escalated into a yelling match. After that, Uncle Rudy's name became a taboo in the Holmes residence and he was nowhere to be seen in family gatherings. However, Mycroft had secretly kept in touch. He was his confidante, the only person who really _understood_.

Mycroft quickly related to him what had happened. He told him about Victor, playing pirates, Eurus becoming resentful and jealous, the dreadful day the poor boy went missing, the _song_ , _the bloody, bloody song,_ then the reference to Drown Redbeard, and Sherlock, traumatized and distraught.

"Uncle, you must come. I'm afraid she'll hurt Sherlock next, and Mummy and Father won't listen. They are still in denial, and I just don't know what to do!" Mycroft pleaded. His voice shook, just as his hand did.

"I'll be on my way right away. Keep an eye on Sherlock until then," Uncle Rudy answered, and Mycroft could hear from the background that he was haphazardly throwing together a travel bag.

"Hurry, please. I don't know what—" Mycroft stopped mid-sentence. He wildly looked around himself.

 _"_ _What is it? Mycroft, what happened?_ " Sensing something wrong, Uncle Rudy urged.

"Fire," the word was whispered from Mycroft's stunned lips. Smoke was rolling down from the upstairs. He dropped the phone and ran up, this time shouting, "FIRE!"

His parents were first to come out, shocked and still half-asleep.

"Mummy! Father! Fire, quick! You must escape now!" Mycroft shouted.

"Where are the kids? Where are Sherlock and Eurus, Mycroft?" Mummy cried out, and Father bolted toward children's rooms. Just then, Eurus came walking towards them, whom Mummy swiftly scooped up in her arms. Eurus' face was serene as always, but Mycroft knew it was her doing the moment he saw the twinkling in her eyes.

"What did you do," Mycroft whispered.

"Sherlock's not here!" Father shouted from the doorway to Sherlock's room.

"He must've gone down using the other staircase. We need to leave now, and find him!" Mummy shouted and began to run toward the staircase closest to them. However, Mycroft stood still.

"Mycroft! What are you doing? We need to move!"

"Mummy, go down with Eurus. Don't let go of her, no matter what. I'll look for Sherlock."

"What do you mean? If he's not here he must be downstairs already!"

"Mummy, just go!" Mycroft shouted. Before his mother could say anything more, he ran toward Sherlock's room.

The room was empty. However, he knew something was amiss. He quickly scanned the room. The torch. The torch that Sherlock kept on his nightstand was missing. So he left by his own will.

Where did he go? It had to do something with Eurus. It must have been some sort of trap, just like it was with Victor.

Mycroft closed his eyes. The fire was spreading, and the smoke was getting thicker. He had three minutes at most. He had to think fast.

Suddenly, a snippet from earlier that day came to mind.

 _"_ _Help!"_

 _Someone was banging on the door to the small storage room at the end of the hallway. When Mycroft opened it, Mrs. Simons, their housekeeper, came out._

 _"_ _Oh thank heavens, thank you, dear. The lock must be broken, it wouldn't open from the inside! Weird, it worked perfectly fine just yesterday."_

 _"_ _I'll tell Father to take a look at it."_

 _"_ _You do that. And tell the little ones not to go in as well, I saw the little miss going in there earlier," Mrs. Simons said as she patted him on the arm._

Mycroft ran to the storage room. Coughing through the thickening smoke, he burst its door open to find unconscious Sherlock collapsed in a loose ball.

The older boy's breathing stopped for a second at the sight, but he was soon relieved by the faint but clear rising and falling of his brother's chest. As Mycroft picked him up, something glittering fell from Sherlock's loose grip. But there was no time to pay attention to it.

Mycroft held him tightly in his arms and started to look for an escape route. The fire had spread at an alarmingly fast rate, devouring everything in its wake. He realized that there was no better way, and ran toward the nearby staircase burning with tall flames. He wrapped himself around Sherlock and tried to shield him as much as he could. The smoke inhalation was a serious problem too. Mycroft did not even want to think about the amount his brother had already inhaled. Flames licked at his back and arms, but he had to go on if he were to save both of them.

At one point debris falling from the ceiling hit Mycroft hard on the back and shoulder, nearly knocking him down. He cried out in pain as he stumbled, but thankfully he could regain his balance quickly and make his way down the last few steps.

"Mycroft! Sherlock!"

Father was waiting at the foot of the stairs. He quickly took over Sherlock from Mycroft and ushered him outside, away from the collapsing house.

Once he was safe distance away from the burning house, Mycroft looked around at his mostly intact family and collapsed.

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A huge thank you to everyone who read & reviewed!


	7. Chapter 6

Here's another chapter! :) Now we are approaching the end.

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As cliché as it was, Mycroft regained consciousness in stages. First, he got his hearing back and could hear distant beeping noises. Then came the unmistakable smell of antiseptics, confirming his suspicion about his whereabouts. He could also feel the scratchy texture of the thin hospital sheet covering him. Judging by the light striking against his eyelids, it seemed to be noon or early afternoon. But then again, it could just be artificial light, in which case the time could be anywhere between morning and late evening.

"If you'd just open your eyes, you won't need to make deductions," a slightly amused voice called out from somewhere to Mycroft's left.

With some effort Mycroft managed to pry his eyes open. It did seem around early afternoon. He gingerly turned his aching head towards the source of the voice earlier.

"Uncle," Mycroft sighed in relief. Uncle Rudy smiled at him sadly from his post beside his nephew's hospital bed.

"Here, drink this first," Uncle Rudy handed Mycroft a cup with a straw.

After his immediate thirst was quenched, Mycroft slowly sat up.

"Is Sherlock okay? He must've inhaled quite a bit of smoke."

"He's okay. The boy is yet to awake but the doctor is confident there would be no lasting damage. It seems everyone got out okay, relatively speaking. You've got some nasty burns and cuts, but they should heal with time," Uncle Rudy said.

Mycroft nodded and closed his eyes, letting relief course through him. He could still remember clearly the image of Sherlock lying unconscious in the smoke-filled room.

After a while, the boy quietly asked, "Was it really her?"

"You know that already, son. Apparently she asked Sherlock to retrieve something from the storage room for her if he wanted to know the answer to her puzzle."

"Eurus," Mycroft moaned as he wrapped his face in his hands. How could she do it? How could she attempt to kill— _burn_ —her sibling? Was it not horrendous enough that she killed one innocent life already? How could he save her, how could he protect her when she was so set on murdering those that did not do her bidding? How could she do that? Didn't she love Sherlock? Didn't she care about others at all? What was Mycroft supposed to do? Condemn her for killing and attempting to kill others? Their brother no less? What was he supposed to tell Sherlock? What do you say to a boy who almost got burned alive by his sister?

Mycroft hated, hated Eurus for what she did and what she almost succeeded in doing. He was appalled that she was capable of such acts of atrocity.

At the same time, he mourned for her, for her evident lack of humanity, for her certain future.

But above it all, he was angry, livid with himself for letting this happen.

"Stop it, Mycroft. None of this was your fault. Stop your thoughts," Uncle Rudy shook his head and gently patted the boy's lowered head.

"Then what am I supposed to do? What am I supposed to do with Eurus? Uncle, she is a murderer! And yet here I am, pitying her like she's some poor misled innocent thing, when she is nothing but a monster. What do you say I do?" Mycroft spat out, his eyes welling with angry tears.

"Sometimes, Mycroft, you'll find that caring is… a disadvantage. Sometimes you just got to eliminate your feelings to make correct judgments. But that is not your burden to bear, at least for now. You just rest and get better," Uncle Rudy said as he stood up, "I'll let your parents know that you're awake. They're at the hotel now, packing things for Eurus."

"Wait, packing? What do you mean?" Mycroft asked, haphazardly brushing away his treacherous tears.

"I told them I'd take Eurus to a facility where she will be kept safe from both outside and herself. Although it took them some time, they came to understand that it's for the best."

"You're taking Eurus away from home? Forever?" Mycroft asked in a shaky voice.

"I'm afraid so, unless she shows some drastic changes in future."

"You can't, she's just a child! A baby, really!" Mycroft pleaded.

"Mycroft. Eliminate your sentiments and _see_. You yourself just said she is a murderer and a monster. You should understand that better than anyone else, as it's you who's been watching her until now," Uncle Rudy stated.

Mycroft was at a loss of words. He knew. Even before Uncle Rudy spoke, deep inside, he knew this was inevitable. If he was truly honest with himself, didn't he already know something like this would happen when he decided to make that call? He knew Eurus was a threat that needed to be contained within utmost security. She was a danger, especially to Sherlock. But still….

"Can I see her? No, I'm seeing her," Mycroft declared as he got out of the bed. "You're right, she needs to be kept in a secure facility. But I'm not going to just lie around when my sister gets sent away."

"Very well," Uncle Rudy sighed. He had hoped to spare the oldest Holmes child from witnessing another tragedy firsthand, but he knew there was no point trying to argue with him.

After getting temporary leave from the hospital, Uncle Rudy helped Mycroft outside to the car park where his car was parked. They drove in silence to the hotel where the Holmes family was staying. When they arrived, Father was coming out with a small luggage in tow.

"Father," Mycroft called as he got out of the car.

"Mycroft," Father said as he approached him to give him a hug. "Are you all right, son?" He asked as he patted him lightly on the back, his relief at seeing his oldest awake evident in the rare show of physical contact.

"Where's Eurus?" Mycroft urged.

Just then, the door to the hotel lobby opened to reveal Mummy coming out with her hand wound tightly around Eurus'. Mummy's eyes were red-rimmed, a clear sign of recent meltdown. Eurus, on the other hand, was calm as ever. When she found her oldest brother waiting for her, she stared at him unblinkingly.

"I'll take her from here. We'll be flying out from a secure location, so I can't take the rest of you with me. Besides, you are needed elsewhere," Uncle Rudy said, approaching to take over Mummy's hold on Eurus. Mummy flinched and instinctively tried to hide Eurus behind her back, but hold herself back at the last second.

"You take good care of her. Promise, Rudy, that you'll take good care of my daughter," Mummy said, fresh tears falling down her cheeks.

"I will, Helen."

Mummy and Father held Eurus close for the last time before they slowly let her go. Even the ever-stoic Father's eyes were red.

"Eurus. I—" Mycroft tried to say something, but he could not finish the sentence. Instead he drew her close and hugged her. He kissed the crown of her head and tried to hold back his emotions. This was it. This would be the last time he got to see his baby sister. Despite his best efforts Mycroft felt his eyes prickling with tears yet again.

Before she released herself from his hold, Eurus leaned in and whispered to him. She then turned around and got in the car, without sparing one glance back at her family.

"I'll let you know when she's settled," Uncle Rudy said before he too got on the driver's side of the car.

The remaining Holmes family stood side by side as the car slowly pulled away from the car park and drove down the road, eventually disappearing from the sight.

 _"_ _I'll see you again, Mycroft,"_ the young girl's last whisper echoed in Mycroft's ears.

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Only two more chapters to go! :) Reviews are much appreciated.


	8. Chapter 7

Now we are moving back to the present! :)

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 _The remaining Holmes family was all present when Sherlock finally blinked open his eyes. At first he seemed disoriented, which quickly turned into a displeased frown upon realizing his current location. He usually liked hospital and all the fancy medical stuff going around there, but hated it when he was on the receiving end of that medical procedure._

 _"_ _Home, now," were his first coherent couple of words after the ventilator was removed and his thirst was sufficiently quenched._

 _"_ _Sweetheart, you need to stay here a little longer until the doctor is sure you are fine," Mummy answered as she carded her fingers through the dark curls._

 _"_ _What happened? Why am I here?"_

 _"_ _There was a fire," Father replied, the unspoken_ Don't you remember? _clear in his voice._

 _"_ _Fire? Hmph. Then why am I the only one here?" Sherlock complained and then narrowed his eyes, "You're hurt, Mycroft. I can see bandage poking out of your shirt. Why are you not in bed like me?"_

 _"_ _I was. Until an hour ago, in fact." When Mycroft noticed the shift in Sherlock's expression from annoyance to concern, he quickly added, "I'm fine, Sherlock. Just some cuts and burns, nothing major."_

 _"_ _And you, Mummy? Dad?" Sherlock asked. It seemed the heaviness of the situation had finally caught up on him._

 _"_ _We are both fine, sweetheart. And Eurus is…." Unable to continue the sentence, Mummy bit her lower lip._

 _"_ _Who's Eurus?" Sherlock asked nonchalantly._

 _Momentarily stunned, the other three Holmes exchanged worried glances among themselves, unsure as to what was happening._

 _"_ _Sweetheart, Eurus is—" Mummy finally opened her mouth to answer, but Mycroft quickly stopped her._

 _"_ _Mummy, don't."_

 _"_ _Don't what?" Sherlock asked with a frown._

 _"_ _Never you mind, little brother. By the way, I got some introductory biomedical books you might like, you being in the hospital and all."_

 _"_ _Give me!"_

 _While Sherlock gleefully indulged in the hardcover books, Mycroft met his parents' eyes and silently shook his head. He did not know whether this was a blessing or a curse in disguise, but he would take it. He would take it and keep it, if it meant his brother was safe and happy._

-Present-

Sherlock was disoriented. When he finally got a hold of himself, he found himself sitting down on the floor with his head buried between his knees.

He blinked, trying to gauge the time passed since his abrupt trip down the proverbial memory lane.

"Now you understand, don't you Sherlock? It is only fair," across from the glass panel Eurus stated in a dreamlike voice.

"What is fair? You're not making much sense," Sherlock snapped. He felt drained and unsettled. His energy was depleted, as if he had just come down from an adrenaline rush or a drug-induced high. He wanted nothing more than to return to the comforting familiarity of London, Baker Street, his flat. And maybe a detour to his brother's office, just because.

"Are you not feeling well? You don't need me to spell this out for you. You're clever."

"Well I just realized that a huge chunk of my childhood memory has been misplaced and I may have re-traumatized myself in the whole process. Seeing as you are the main source of that trauma, of course I'm not feeling well," Sherlock growled.

"You sound upset. Why are you upset?" Eurus asked wonderingly.

"Never mind," Sherlock said impatiently, "if Mycroft couldn't get you to understand sentiments, then it's a lost cause. It's beyond your understanding. Now stop wasting time and answer the damn question. What it is that I'm supposed to understand now?"

"You asked me why I wanted to kill Mycroft. It's simple; Mycroft kept you alive and well. You got his life. So it's only fair that I also get something of his."

"Get what?" Sherlock asked. As soon as he uttered the question, the answer dawned on him.

Eurus looked into Sherlock's eyes. She too knew that Sherlock had already figured out the answer to his own question. Nonetheless, Eurus whispered the answer as if she was sharing a secret.

"His death."

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We only have one more chapter to go. Huge thanks to all of you who read & reviewed!


	9. Epilogue

I'm so sorry for the long wait! Here's the final chapter.

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When Mycroft returned from a meeting, he found his brother waiting for him in his office. Sherlock did not greet him as he came in and sat down behind his desk in his chair. Mycroft arched an eyebrow at him in a silent question, but a deep scowl was the only thing he got in return. The older brother rolled his eyes in an obvious show of great suffering.

"Okay, I'll bite. Why are you here, Sherlock?"

"I remember now."

"Remember what, pray tell?"

"You. _All through the night_. Everything."

"Oh."

"Oh? That's all you got to say? _Oh?_ "

"Well, what do you want me to say? It's all in the past, Sherlock. You remembering it or rewriting it doesn't really change a lot."

"It does!"

"Exactly _what_ does it change?"

"Well, maybe the fact that you apparently have promised your _death_ to our sister! Really, Mycroft, of all people I've never seen you as the suicidal type."

"Is that what this's about?" Mycroft asked. When Sherlock pursed his lips and refused to answer, he rolled his eyes for the second time. "Don't be so dramatic about it, Sherlock. You and your drama, really."

"So you're not denying it? Are you _mad_? You must've gone senile to promise her that! What in the bloody hell were you thinking?!" Sherlock roared.

"Sherlock. Death is inevitable for everyone. Eventually I'll die one way or the other, and frankly I have no real preference in that matter. Besides, you've seen her. Uncle Rudy and I have basically robbed her of any chance at normality. Her whole life has been snatched from her. At the very least she should be able to choose her own death."

A realization dawned on Sherlock.

"…She will be killed when you die."

Mycroft sighed.

"Yes. The only reason 'people upstairs' are letting her live despite the potential threat she poses against our nation is because I vouched for her. I promised them I could keep her in line and get her assistance when needed. So when I'm dead, there will be an immediate order to remove the unmonitored threat."

"So you'll just die whenever she feels like ending her life? What are you two, some sort of symbiotic soulmates?" Sherlock scoffed.

"You have no right to question my decision," Mycroft answered in a hushed voice. "You weren't there, Sherlock. You weren't there to see her grow up inside that facility. Imagine a little girl, confined in isolation and treated like a lab animal."

"No lab animal gets a _Stradivarius_."

" _The point is,_ I am in no position to deny her this little request. Not after everything I've done to her."

"And what exactly have _you_ done to her? It was her choice, Mycroft! It was _her_ choice to kidnap and kill Victor, it was _her_ choice to burn down Musgrave! May I remind you that I almost _died_ in that fire? You didn't force her to do any of these things, why do you feel responsible for them? You're deluding yourself because you're still in denial that our sister is a psychopathic monster!"

"Sherlock!"

"Face it, Mycroft! She is a monster. And I'm not going to lose my brother to her," Sherlock stated fiercely. "Try all you might, but you're not dying, not on my watch." Sherlock's voice was pained. He knew the gravity of the promise, now more than ever. He was still haunted by the dying image of Mary Watson. But he was still making the vow, because he could not _not_ do it.

"…Enough of this, Sherlock. I've got things to do, and I'm sure you've got things to blow up back in your flat."

"Well too bad, I'm not leaving till I hear you say it."

"Say what?"

"That you won't foolishly throw your life away at a call from Eurus."

"Sherlock."

"Say it."

"You are being childish—"

"Say. It."

Mycroft pursed his lips. He refused to speak anymore, his steely eyes glinting like they did when he refused to pull the trigger on the governor at Sherrinford.

Sherlock crossed his arms, equally defiant. "Fine, then I'll say it. You will not kill yourself or let yourself be killed, because then that will be the end of the Holmes line," he said.

"Sherlock," Mycroft said warningly.

"Just think about it rationally, Mycroft. Do you really think Eurus will willingly accept death when you do? Who do you think can possibly defeat Eurus after you're gone? Your security team? MI6? Please. They won't come even close to a match to Eurus. But if you die because of her, I promise you I'll dedicate my whole life to bring justice upon her. It will very likely be the demise of both of us. So, dear brother," Sherlock grinned a devilish grin, a pirate's grin, "stick to your diet and stay healthy. You need to outlive her and me, and you've already got a huge disadvantage in age."

Sherlock stood up without further ado and showed himself out. His whistling of the familiar tune of lullaby echoed through the quiet hallway.

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Again, I'm so, so sorry for not updating for months! I'm really bad at finishing stories... in fact, I think this is actually the first multi-chapter fanfic that I saw through to the end. Thank you all for reading (and reviewing!) this story. I hope I will be able to bring you another story (not sure which fandom) soon!


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